Welcome to the forum, Bradley.
Well, the guitar is in Brooklyn and you are in NYC, too? So you can look at it in person, right?
I agree that it would be a neat guitar, if everything works right and if the modifications are truly reversible. If you go look at it, make sure the pickup cavity route was not made slightly larger when they installed the mini humbucker. Get a 6" metal rule marked in 32nds and 64ths, then measure the width and depth of the original pickup. Measure the width and depth of the hum bucker surround. If they are the same and the pickup cavity route doesn't look enlarged, then you are in good shape vis a vis the reversibility issue.
I wonder if that bridge pickup is a single pole or a humbucker. If it's a single pole pickup, it's going to have some hum to it compared with the neck pickup. That may or may not bother you. The bridge pickup and switch appear to mounted on the pickguard. Again, if there are no markings under the pickup, you are in good shape with that issue.
One thing bothers me on this guitar is that the bridge top is all the way down, bottomed-out, i.e., can't be adjusted any lower. This reminds me of an unfortunate problem I had with an M-65: The hollow laminate body had caved in under the pressure of the string tension!
My guitar was an early '70's model. It was extremely clean, with a shiny black finish and an engraved harp tailpiece. I thought it was a really cool light-weight guitar, until I couldn't get the action down. I took it to my luthier, who showed me that the body had torqued (caved in) under the pressure of the string tension. The symptoms were that the break-over angle was very mild (too shallow) and that, while the bridge top was slammed down as far as it could go, the action was still too high. You could play cowboy chords, but not up the neck.
My luthier said there were two fixes; re-set the neck to treat the symptoms of the the body problem, or attempt to re-torque the body, by applying tension to the guitar in the opposite direction of the normal string tension. The neck was in good and tight, so steaming the neck out would have really affected the finish. Re-tensioning the body might have worked, but it was also going to crack the finish. So, both fixes were going to hurt the value of the guitar and I didn't attempt the repair(s).
I didn't think much of it until a couple of years ago, when I bought a '60's Starfire III that had the same problem, a 'torqued' body. This time the finish was so beat-up that I opted for the neck re-set option. While the repair turned out well, pulling the neck on a guitar that doesn't need it can be problematic. With the Starfire, a 3" piece of the side laminate pulled off when the neck came out! Again, the guitar was so beat-up that when the loose piece of laminate was glued back you couldn't even see the repair, even when you were looking right at it!
Finally, the M65 was always a beginner's guitar. You can doll 'em up, but they don't have the value of the more professional grade instruments. Caveat Emptor, Let the Buyer Beware!
